Roof Gardens

I remember once one holiday ascending one of Rome' seven hills and looking down from its slopes onto the roofs of the Eternal City, which has been a crowded urban area for over two millenia. In a city centre where there are few urban gardens, one citizen had established a small garden space atop a flat roof. It was not a lush jungle, but a leisure garden, with table and chairs and a network of flowers,which from a distance seemed to be roses. A small sapling grew in a pot. It was an ideal amenity garden on which to sit in a warm Italian evening, above the incessant roar of the traffic in the city which in ancient times never slept. This little garden, not famous to the world, was someone's paradise, their little Eden above ground, but below the clouds, where they would sip wine and enjoy the peace.   

The roof garden is  a particular form that combines green roof with container garden, and it is related to the green balcony, which is subject to the same technical rules as a green roof. To construct a roof garden you need to have easy and safe access to the roof, probably through an internal staircase which opens onto a roof door. You also need a parapet or some kind of secure barrier to protect you from falling from the roof, for there is no leisure in a  dangerous space. This is especially so if you have children, for whom any parapet should be strengthened by secure netting. But I would not put pots or plants on the parapet, as they could be hazard to people below if they are blown off by wind. In fact, you need to ensure that there is nothing that can be blown away, as the higher you go the less protection from wind you have.

Of particular importance is loading. Roofs and balconies are  designed only for so much weight, and so some people planning roof and balcony gardens consult a structural engineer to assess whether it is possible to have them and if so  how much weight is possible. You see, there is a problem not widely known to non-engineers,  which I only found out through studying gardening, that  excessive weight on a roof can exert a downward and outward pressure on the walls, so weight needs to be kept light. 

Take a look at the picture below, and you see a roof garden with raised beds, but note that the sides of the beds are small, limiting the weight of wood on the roof, and the plants are not not of excessive size and weight. You are seeing an example of a very well-constructed roof garden. Note also  that there are good, strong parapets along the sides of the roof for protection. There is what appears to be fertilizer on the soil, and this suggests that the gardener is avoiding large  applications of manure, which can be heavy when wet, in favour of  a lighter soil, and adding fertility by the use of not only fertilizer, but pelleted manure,which is light and has a high level of nutrients per volume.  

A simple garden might make use of roll outs, which are mats seeded with wild flowers about which there was an article on Wizzley by Blackspanielgallery, the title being A Garden Made Simple. These have the advantage of being ready made and quite light, as they do not contain much soil, and as wild flowers do not use many nutrients [in fact they do not like nutrient-rich soil] they do not require much feeding. One advantage is that these roll outs do not require containers and therefore impose less strain on the roof than containers do.  

Kitchen gardens on roofs are possible, though deep rooted vegetables such as potatoes and parsnips are possibly difficult in any bulk. In fact, you don't want bulk plantings, like potatoes, but lighter, specialist ones, for example a herb garden. Herbs like quite light, well drained soils and are not on the whole heavy. I have heard that somewhere in London there is a chef who grows his herbs in a roof garden. 

A herb garden on the roof is ideal, There are four main  families of herbs. First is the Umbellifers. These include parsley, sweet cicely , coriander, chervil and fennel. This family includes basil, sage and thyme. Then there is the Mint family, with all the rich varieties of mint. We  find the liliaceae, the lily family, whose edible members include garlic, chives leeks and onions. The Brassica family include mustard and horse radish.  The fifth main herb family is ginger, but that is a tropical tree and so not suitable for roofs or a colder climate. 

Yet a roof garden can also provide a rich range of salad vegetables,planted in succession. And one great advantage is that the roof is freer of perennial weeds than the soil is. you will not find bindweed in your pots. The roof is therefore a controlled environment. You might even have a greenhouse, ideally a fabric one to save weight, and some roofs. This would give you tomatoes, cucumbers and melons. 

But for many people their roof  is a sanctuary, a place to sit above the hustle of the city. They enjoy a rich network of flowers. These will not be densely packed, for they will be laid in light containers separated by paths. Roses are very popular, but there can be a whole range of flowers according to taste. In this sense a roof garden has an advantage over a balcony, as balconies can be shaded. Only recently I was visited by a young lady from Buenos Aires [seeing my youngest son] who told me that she would love to grow something on her balcony, but it was too shaded. My solution: I went to my book shelf and gave her Plants for Shade. I needed it when taking my gardening certificates, but never since then, as shade is not an issue for me. I am promised that she will send me a picture of her balcony. 

But roofs can be a safe space for bees. The city tends to be free of the worst pesticides that are decimating bee colonies. It is also replete with flowery gardens. Bee heaven! Yet another advantage is that bees dislike dogs and horses, neither of which are common on roofs. Dogs maybe on occasion, but when did you ever see a horse on a roof? Cats, maybe, but bees do not dislike them as they dislike dogs

The choice before humanity is a green future or no future. We are going to have to get a grip of our environmental problems, and we must do so in a world where there are great cities. That is unless population slumps dramatically, which would be a disaster. Green roofs, green balconies and green walls are all part of the CO2 absorption strategy. Moreover, psychologists are becoming increasingly aware of the need for greenery in human lives. We need green spaces to look at for our mental health. Hospitals now need green spaces as they know that patients heal quicker when they see greenery than when they do not. The emotionally and philosophically impoverished view of humans as consumers whose prime need is material goods provides a shriveled life for its victims.We need a view of humans that sees them as primarily spiritual and moral creatures. It was for this reason that mediaeval Christians saw gardening a high activity. 

Roof gardens are part of a wider, more sophisticated answer to the needs of  urban humans. We need to design at least some of our roofs with the possibility of roof gardens in mind.Let us have a life in which gardens spring up in as many nooks and crannies as possible.